Russian sports minister Vitaly Mutko warns more athletes could test positive for meldonium

Tennis star Maria Sharapova claimed she had been taking the drug for 10 years for medical reasons as she admitted failing a drugs test at the Australian Open.

Mutko said the drug, manufactured in Latvia, is popular among the country's athletes and warned of further revelations to come.

"Maybe this will wake our trainers and federation up a bit. Unfortunately, a lot of athletes took this medicine,” he told the Russian agency R-Sport. "There won’t be a huge wave but I suspect there could be several more cases.

“This medicine used to be allowed, it does not do anything major, it just helped a lot of people with their recovery times; it did not offer any unfair advantages.”

Russia's short-track speed-skater and 2014 Olympics champion Semion Elistratov and five-time world champion skater Pavel Kulizhnikov have tested positive for the presence of meldonium, according to R-Sport.

Alexander Markin, a member of Russia's national volleyball team and the Dinamo Moscow volleyball club, also tested positive for meldonium, R-Sport news agency quoted the Volleyball Federation of Russia as saying on Tuesday.

"Markin's case will be reviewed on April 19 by the International Volleyball Federation (FIVB)," R-Sport cited Alexander Yaremenko, federation secretary-general, as saying.

Meanwhile, the Latvian company which makes meldonium revealed to Associated Press on Tuesday that the normal course of treatment for the drug is four to six weeks, rather than the 10 years that Sharapova says she used the substance for.

"Depending on the patient's health condition, treatment course of meldonium preparations may vary from four to six weeks. Treatment course can be repeated twice or thrice a year," the company said in an emailed statement.

"Only physicians can follow and evaluate patient's health condition and state whether the patient should use meldonium for a longer period of time."

[RELATED: WHAT NEXT FOR SHARAPOVA?]